The executions were carried out at 12.35am local time (3.35am AEST) on Nusakambangan prison island. But it took up to 27 minutes for all the prisoners to die, with a spokesman for the Attorney-General Tony Spontana saying they were "shot at 00.35 and died at 01.02."

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A source said all prisoners died after being shot in the heart and it was not necessary for the commander to shoot anyone in the head, as is the case if prisoners don't die after 10 minutes.

A woman places a candle on top of pictures of the executed prisoners at a vigil in Sydney.Credit:Getty Images

All eight prisoners refused blindfolds and met their fate staring straight ahead, joining together to sing hymns including Amazing Grace as the shots rang out, according to one one the priests who witnessed their executions.

"Everyone was looking forward, it seems everyone accepted their fate," said Father Charles Burrows, who provided spiritual guidance to Brazilian man Rodrigo Gularte.

"We respect Indonesia's sovereignty but we do deplore what's been done and this cannot be simply business as usual. For that reason, once all the courtesies have been extended to the Chan and Sukumaran families, our ambassador will be withdrawn for consultations.

Mary Jane Veloso was spared the firing squad last year.

"I want to stress that this is a very important relationship between Australia and Indonesia but it has suffered as a result of what's been done over the last few hours."

Andrew Chan's brother, Michael, took to Twitter on Wednesday morning to express his grief.

We respect Indonesia's sovereignty but we do deplore what's been done and this cannot be simply business as usual.

Tony Abbott

"Today we lost Myuran and Andrew," the Sukumaran and Chan families said in a statement.

"Our sons, our brothers. In the ten years since they were arrested, they did all they could to make amends, helping many others."

The family said they asked for mercy, but there was none. "They were immensely grateful for all the support they received. We too, will be forever grateful."

Australia's Consul-General for Bali, Majell Hind, will formally take possession of the bodies of Chan and Sukumaran on Wednesday before they are transported by ambulance to a funeral home in Jakarta.

Families of the duo will follow the ambulance on the 12-hour journey. The bodies are then expected to be flown back to Australia on Friday morning.

Veloso spared from the firing squad

Mother-of-two Veloso was supposed to be shot along with the rest of the condemned prisoners, but a last-minute development in her case saw her execution postponed.

Attorney-General spokesman Tony Spontana said Veloso's execution had been postponed because of the Philippine president's request in connection with the human trafficking suspect surrendering herself in the Philippines.

He said Veloso was required to provide her testimony.

Veloso, a maid who was arrested smuggling 2.6 kilograms of heroin into Yogyakarta, always maintained she was innocent and was not aware there was drugs in the lining of her suitcase.

She said she was set up by her godsister Kristina, who allegedly bought her a suitcase and new clothes in Malaysia and told her a job as a domestic helper was waiting for her in Indonesia.

Veloso's recruiter, Maria Kristina Sergio, reportedly surrendered to authorities in the Philippines on April 28, the day Veloso was due to be executed.

Mr Spontana said Veloso would need to give evidence in the court case.

Tears, songs mark emotional vigil

Relatives and friends of the condemned were in a tent near the killing field and became hysterical when the shots were heard, a source told Fairfax Media.

Among those in the tent were Chan and Sukumaran's Australian lawyer, Julian McMahon, Bayside Church senior pastor Christie Buckingham and Salvation Army minister David Soper, who were allowed to spend precious last hours with the Australians.

Jakarta newspaper attacks death penalty

"What is the use of executing people for Indonesia? It will create much more harm than good," the paper wrote.

"The fact is that executing has nothing to do with drug eradication. Before carrying out the death penalty, we must fix our law enforcement agencies, and the prison and judiciary systems.

"We have to make sure first that these systems will allow us to arrive at the correct ruling. Without certainty that our system has minimum flaws, we can't execute people."

The paper reserved particular criticism for Mr Widodo for insisting on the death penalty even after overwhelming legal and political pressure for clemency, both domestically and internationally.

"Joko has made statements that prevent him from changing his stance. He publicly stated that he would not grant clemency to drug offenders. Thus, he had already made a decision before reviewing each case.

"This was a mistake, and backpedaling (sic) may be in the best interest of Joko and the nation."

The editorial was written before the executions overnight, but still called for a last-minute reprieve.

"Joko must delay the execution until he reviews each case," it said.

"There is no shame in accepting and correcting one's mistake. This is not a sign of weakness. Rather, it is a sign of greatness. This is wisdom that will put him as a great leader."